"Results of nasal and lung swabs have tested positive for influenza B," it reads. Influenza is more commonly known as the flu.

Seven days after he was taken into CBP custody, Felipe was pronounced dead at the Gerald Champion Regional Medical Center in Alamogordo, New Mexico, on Christmas Eve after exhibiting flu-like symptoms, including a high temperature and vomiting.

"While this result indicates that the child had influenza, determining an accurate cause of death requires further evaluation of other laboratory specimens and interpreting the findings in the context of the symptoms and autopsy findings," continued the medical examiner's statement.

Felipe crossed the border near El Paso, Texas, with his father, Agustín Gomez Perez, on Dec. 18. The boy's half-sister told media that Gomez Alonzo had hoped to come to the US to earn money and pay off thousands of dollars in debt, some of which had come from a loan to help the pair get to the States.

Luis Echeverria / Reuters

Women make an altar with pictures of Felipe Gomez Alonzo at the family's home in the village of Yalambojoch, Guatemala.

"He was going to work to repay the loan and give his son a better future," Catarina Gomez Lucas, the 21-year-old daughter of Gomez Alonzo, told CNN. Instead, within a week the boy was dead.

Gomez Lucas told the Washington Post that news around the village was that adults arriving across the border with a child were more likely to remain in the US, and that's why the father chose to take one of his three sons.

His mother, Catarina Alonzo, speaks only Chuj, a Mayan language, and his father speaks Chuj and some Spanish. They live in a one-room wooden shack in Yalambojoch, in remote western Guatemala, about 1,800 miles from El Paso.

Gomez Perez earned less than $5 a day as a farmworker. Felipe sometimes helped his father work, and also enjoyed reading and soccer, said his sister. He was excited to go to school in the United States and also to get a bicycle, like another child in the village had gotten after his father went to the US. "It was his dream," she said.

The pair had left home two weeks ago, and Gomez Alonzo did not seem to have any obvious health problems on the long journey to the US.

“My father doesn’t know what happened,” Gomez Lucas said. “He was well. He was happy. He was playing.”

Just weeks earlier, a 7-year-old girl died hours after she and her father were taken into custody by CBP agents in New Mexico after crossing the border.

In response to the children's deaths, CBP announced it would be conducting secondary medical checks on all children in its care, particularly those under 10, and would be seeking help from other agencies to improve its medical care.

Luis Echeverria / Reuters

Catarina Alonzo at her home with her son Oliver.

Gomez Lucas said that the family wanted Felipe's body to be returned to them in Guatemala so that he could be buried there. But they also wanted his father to be allowed to remain and work in the United States so that "my brother’s death won’t be in vain."

CBP did not respond to BuzzFeed News' request for news about the father's whereabouts and if the boy's body would be returned to Guatemala.

His mother, Catarina, told CNN that she wanted her husband to work in the US.